In a risk assessment study done by Almeida et al. (2013), the FISK tool scored a high-risk impact for S. glanis, given the enormous predation potential of this species. Moreover, S. glanis is in the high-risk score category (lower region) of potential pests in ENSAR (European non-native species aquaculture risk assessment) according to its risk of introduction, establishment, dispersal, and impacts, although this may be variable according to context (Copp et al., 2009). Because it is in part native to Europe, S. glanis is not included in the Invasive Alien Species of Union concern, however, Invasive Alien Species Regulation (Regulation (EU) 1143/2014) invite each member state to develop their own list of IAS of national concern.
In Italy, the first record of S. glanis was in 1957 in the Adda River (northern Italy). It was a single individual, probably escaped from a put and take lake in the occasion of an exceptional flooding. The first self-established population was then recorded in the Po River at the end of the 1960s (Gandolfi & Giannini, 1979). Since then, the species has spread in all major river basins of north Italy (De Santis & Volta, 2021), central Italy and has invaded also the largest southern Italian basin, the Volturno river basin (De Bonis et al. 2015). Due to its wide distribution in Italian peninsula and the decline of several prey species detected after its invasion, the species poses a serious risk for the national biodiversity and therefore several regulatory and conservation efforts have already took place., the species has been included in project-supporting legislative tools started to consider this and other invasive species as a national priority. For instance, LIFE 15 GIE/IT/001039 ASAP developed and sent to the Italian Ministry of the Environment a proposal for the IAS national blacklist, including s. glanis and classifying it with the maximum score regarding invasiveness and with 14/15 points as overall level of priority. Also, LIFE GESTIRE2020 included it among the worst invasive alien species in freshwaters (Tamborini et al., 2019). From a regulatory point of view, to prevent this unwanted invader from expanding, Lombardy (LR 31/2008; RR 2/2018) and Piedmont (LR 37/2006) Regions have regulated catfish as prohibited, imposing a ban on both introduction and release of the species, making it mandatory to kill the caught catfish.
Control and eradication campaigns have been carried out in Italy for instance in L. Comabbio and L. Varese but most of the conservation efforts have been targeted so far riverine ecosystems in Italy, while no other projects specifically targeted catfish in large lakes and reservoirs.
In Portugal, the species was first introduced in 2008, in the Tagus River, as indicated by citizen science records (Gago et al. 2016). Nevertheless, the first official record was in 2014, when local fishermen captured two individuals in the Tagus River (Gkenas et al. 2015). At present, the species is restricted to the Tagus River Basin, where it inhabits both lotic and lentic environments (Ferreira et al 2019). However, given the increasing number of new introductions and range expansions of the species in the Iberian Peninsula, and the growing interest by recreational fishermen (Gago et al. 2016), it is highly likely that other basins will be colonised in the near future. For example, citizen science data indicate the presence of catfish already in the Douro River (Martelo et al., 2021). Moreover, the Guadiana River basin may be colonised by individuals from neighbouring drainages, such as the Guadalquivir River basin, where the species has recently been recorded (Sáez-Gómez and Prenda, 2019), or from the Alqueva reservoir, which has been the recipient of several new non-native fishes (Banha et al., 2017).Because of its fast spread and the already reported impacts on Portuguese native biodiversity, S. glanis has been included in the national blacklist (Annex II) of the Decreto-Lei nr. 92/2019, forbidding its transport and detention, and within the legal framework of the Portuguese inland recreational fisheries law (Decreto-Lei nr. 112/2017), anglers and professional fishermen are requested to euthanize this IAS once caught.. Currently, control and other management actions are not carried out systematically in Portugal, but a National Plan for the Catfish Control is under developing, which aims to propose management actions for the species control and communication approaches to prevent the further spread of the species and mitigate its impacts.
Despite regulatory and management actions took already place, and despite the invasion history is different between Italy (long) and Portugal (recent), in both countries the species keeps spreading in new ecosystems and, considering the strong fragmentation of the main rivers of northern Italy and of the Tagus River in Portugal, it is highly likely that the colonization of lakes and reservoirs is mainly attributable to voluntary releases by recreational fishermen, since this fish is considered a valuable resource among them due to the large body size reached.